Decarboxylation Reaction of α-Methyl Amino Acid Catalyzed by Aromatic L-Amino Acid Decarboxylase from Micrococcus percitreus

Abstract

The decarboxylation of L-tryptophan catalyzed by the aromatic L-amino acid decarboxylase from Micrococcus percitreus was competitively inhibited by α-methyl-L-phenylalanine. During prolonged incubation with the α-methyl amino acid, the enzyme lost its activity and its absorption spectrum changed drastically. The activity was restored by the addition of a cofactor, pyridoxal phosphate (PLP). The reaction products from α-methyl-L-phenylalanine were isolated and identified as methylbenzylketone and α-methyl-β-phenylethyl amine. PLP added to the reaction mixture was found to change to pyridoxamine phosphate (PMP) after the reaction. These results indicate that the enzyme catalyzes decarboxylation-dependent transamination besides the normal decarboxylation of α-methyl-L-amino acids.